1. Field of the Invention
The present invention relates generally to charging devices, and particularly to wireless charging devices.
2. Technical Background
Portable or hand-held electronic devices have become ubiquitous. Moreover, the communications and computing technology spaces over-lap with modern cell phones and lap-tops, tablets and I-pads having much of the same. One reason that these devices are so popular relates to the fact that they can be carried and used by the user almost anywhere. Thus, a user can make telephone calls, send and receive emails, exchange text messages and/or browse the internet on the fly. In order to support such device mobility, each of these portable electronic devices must include some type of rechargeable battery system (e.g., electrochemical batteries, capacitor batteries, etc.). As a result, there is an urgent need in the market for battery recharging stations.
In one approach that has been considered and tried, many electronic devices are commercialized and sold together with their own charging means. To be specific, many charging devices of this type are configured as an electrical power cord that has a set of electrical contacts disposed in a DC output plug that has a form factor configured to mate with a corresponding charging receptacle formed in the portable device. The charging cords (or stations) of this type are configured to be connected to an AC power source (e.g., 120 VAC) and convert the AC power into a low voltage DC signal that charges the battery. One drawback to this approach is that the charging cord/station is only usable with that particular device. Thus, its unique DC interface cannot be used with any of the other portable devices on the market because they have charging receptacles with a different form factor. As a result, when one of the charging station or the portable device gets damaged or has reached end of life, both have to be replaced.
In another approach that has been considered, a portable charging station includes an AC power connection (that couples the device to AC power) and is further equipped with one or more standardized low voltage ports (e.g., USB ports). While the portable electronic device is also equipped with a standardized low voltage port, it may not necessarily have the same form factor or configuration. In either case, the user must obtain a low voltage cord that is appropriately terminated on each end to charge the device. That cord must then be stowed when it is not in use. While this approach goes a long way toward solving the universality issue, it does not totally solve the problem; the so-called standardized low voltage ports actually comprise a family of low voltage port standards. One drawback to this approach therefore relates to the user's accumulation of low voltage cords over time. (One for each type of portable device in his possession). Many users will reach into a drawer for the “right” low voltage cord, only to pull out a plurality of tangled cords that must be separated. Once the cords are separated, the user must “eye-ball” the various cords and select the right one for the device he is seeking to charge. As a result, these charger types are susceptible to being misplaced, lost or stolen.
Perhaps as a result of the aforementioned issues, many portable charging stations now include “wireless power transfer technology” that eliminates the need for a low voltage interconnection cable. Specifically, a device is charged using wireless magnetic inductive coupling; the charging station includes a coil winding and the portable electronic device is equipped with a secondary coil. The two coils form a transformer. Charging occurs when the portable electronic device is brought within range of the charging coil's magnetic field. While this approach simplifies the cord entanglement issue, it also presents other drawbacks. While the low voltage cable is eliminated, the charging station still requires an AC power cord and further requires a charging cradle that positions the mobile device proximate the charging coil. Thus, the resultant charging station is bulky and unwieldy, making it inconvenient to cart around and stow. Moreover, wireless charging stations are also susceptible to being misplaced or stolen.
These various approaches all require that the charging device have a power plug to receive power. Another problem arises when the power is derived from an electrical wiring device which is a class of devices installed in an outlet box as part of an electrical distribution system. When the charging station is plugged into the electrical wiring device, that particular voltage port is no longer available for any other use. Also, the power plug or the charging device itself obscures the face of the wiring device, effectively taking part of the wiring device out of service.